This application claims priority to Japanese Patent Application No. JP 2001-178855, filed on Jun. 13, 2001, the disclosure of such application being herein incorporated by reference to the extent permitted by law.
1. Field of the Invention:
The present invention relates to a chemical mechanical polishing apparatus (hereinafter referred to as CMP apparatus). More particularly, the present invention relates to a CMP apparatus featuring a configuration of a polishing pad thereof.
2. Description of the Related Art:
As a result of increasing integration of LSI chips, internal wiring configuration has become still finer along with further multiplication of wiring layers. Because of this, in the production of a semiconductor apparatus, a technology for fully leveling off or smoothing a wafer surface has become an important issue to be taken into consideration. As a countermeasure for solving such leveling issue, such an art for leveling off the wafer surface by applying chemical mechanical polishing method has been practiced. As schematically shown in FIG. 4, for example, a conventional CMP apparatus utilizes a rotary platen 1 having attached thereto a porous polishing pad 6 made from foamed urethane resin, for example. This system feeds slurry 7 composed of aqueous solution containing polishing agent such as silica to the polishing pad 6 via a nozzle. For example, a wafer is secured to a vertically movable head 7 via a cylinder. While pressing the wafer against the polishing pad 6, the wafer is polished with slurry 7 by way of rotating the platen 1 and the head 7.
FIGS. 5A and 5B schematically shows a conventional polishing pad 6 utilized by a conventional CMP apparatus. FIG. 5A designates a plan view, whereas FIG. 5B designates a lateral view thereof. As shown in FIG. 6A, the polishing pad 6 has disc-shaped configuration. As shown here, the polishing pad 6 is rotated in a clockwise direction when viewed from top in the figure, for example, at a revolving speed of approximately 50 to 150 rpm. The Slurry 7 is fed to the substantially central portion of the polishing pad 6 at a feeding rate of 100 to 300 cc/min., for example. After being fed, slurry 7 spreads itself over the pad surface via centrifugal effect generated by the rotating the platen 2. While this condition is kept, the head 1 is pressed against the polishing pad 6 with constant pressure so that the head 1 can be rotated to polish a wafer secured to the head 1 whereby leveling off the wafer surface.
During or after the polishing process, while applying pressure to the polishing pad 6, a dresser 3 shown in FIG. 5 is rotated itself to come into contact with the polishing pad 6 in order to provide the surface of the polishing pad 6 with sawing function.
On the other hand, while operating the above conventional CMP apparatus to execute a polishing process, a problem as cited below may occur. That is, the slurry 7 fed to the polishing pad 6 helically diffuses towards a peripheral edge of the surface of the disc-form polishing pad 6 from the center portion and then leaks or falls outwardly from the peripheral edge thereof to result in waste of the slurry material.
In view of such problem, there is a proposal for preventing the slurry 7 from outwardly falling from the peripheral edge of the polishing pad 6 by way of banking the peripheral edge thereof. FIG. 6A designates a plan view of a conventional polishing pad with such feature, whereas FIG. 6B designates a lateral view thereof.
As described above, the above method for polishing a wafer surface by way of feeding slurry 7 into the polishing pad 6 is effective to minimize waste of slurry material 7. On the other hand, inasmuch as slurry 7 is constantly held inside of the polishing pad 6, when setting the sawing function of the polishing pad 6 with the dresser 3 after completing the polishing of the wafer, the polishing pad 6 cannot properly be adjusted for setting the sawing function under the existing state. Further, inasmuch as part of ingredients contained in the slurry 7 coheres itself without allowing to wash it off, it is very likely to cause the wafer surface to incur undesirable scratch, thus raising a critical problem.
Japanese Laid-Open Patent Publication No. HEISEI-11-58218 (1999) discloses another art which proposes such a polishing pad and a polishing apparatus comprising such a system in which a polishing pad is provided with a through-hole for feeding polishing solution (slurry) and another through-hole for discharging slurry to enable the system to discharge slurry simultaneously with a process of feeding slurry thereto.
According to this art, although it is certain that the above-cited problems can be solved, it is required to provide the polishing pad with a specially configured construction whereby resulting in a considerably complicated construction, thus incurring increased cost as a problem to be solved.
The present invention has been conceived in view of the above mentioned problems by providing a novel CMP apparatus which is configured with a simplified construction that may be capable of minimizing cost and consumption of slurry, and yet, capable of securely washing slurry off from the polishing pad.
According to a first preferred embodiment of the present invention, there is provided a polishing apparatus for polishing an object by causing a polishing pad and the object having rotation relative to each other to be abutted to each other via slurry; the chemical mechanical polishing apparatus includes a plurality of slurry stoppers individually positioned across substantially equal angular intervals along an external periphery of the polishing pad and the plurality of slurry stoppers are positioned by determining a predetermined interval on the polishing pad.
According to second preferred embodiment of the present invention, there is provided a polishing apparatus for polishing an object by causing a polishing pad and the object having rotation relative to each other to be abutted to each other via slurry; the chemical mechanical polishing apparatus includes a plurality of slurry stoppers individually positioned across substantially equal angular intervals along an external periphery of the polishing pad and each of the plurality of slurry stoppers are individually disposed obliquely against a direction of rotation of the polishing pad.
According to still another preferred embodiment of the present invention, there is provided a polishing apparatus according the second preferred embodiment, in which the plurality of slurry stoppers are individually disposed by being slanted by an angle relative to a direction of rotation of the polishing pad determined according to a rotation speed to which the polishing pad is submitted.
According to still another preferred embodiment of the present invention, there is provided a polishing apparatus according the second preferred embodiment, in which the plurality of slurry stoppers are individually disposed by being slanted by approximately 5 to 45 in relation to a direction of rotation of the polishing pad.
According to still another preferred embodiment of the present invention, there is provided a polishing apparatus according to any of the above mentioned preferred embodiments, in which the plurality of slurry stoppers are attached to the polishing pad.
According to the preferred embodiments of the present invention, it is possible for the inventive (chemical mechanical) polishing apparatus to minimize consumption of slurry by applying a simplified construction, and yet, allow a dresser to set saw and wash off slurry without considerable obstruction. Further, inasmuch as slurry is prevented from cohering itself, unwanted scratch on the wafer may be prevented.
The novel (chemical mechanical) polishing apparatus according to the preferred embodiments of the present invention may also be realized merely by attaching a plurality of slurry stoppers to the polishing pad, and thus, it is possible to manufacture the inventive polishing apparatus at comparatively reduced cost by way of utilizing a conventional polishing pad.